Preparation of unsaturated nitriles



Patented Oct. 10, 1939 UNITED STATES PREPARATION OF UNSATURATED NITRILES Donald J. Loder, Wilmington, DeL, assignor m E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation oi. Delaware No Drawing. Application November 22, 1934, Serial No. 754,338

3 Claims.

This invention relates to a process for the preparation of unsaturated nitriles and more particularly to the preparation of alkyl acrylonitriles, to the preparation of the methyl acrylonitrile, and to the conversion of the alkyl acrylonitriles to the alkyl acrylic acid esters and their derivatives.

An object of the present invention is to provide a process for the preparation of the alkyl acrylonitriles. Another object of the invention is to provide a process for the conversion of the alkyl acrylonitriles to derivatives of the alkyl acrylic acids and more particularly to the alkyl esters of methacrylic acid. A further object of the invention is'to provide aprocess for the preparation of the alkyl acrylonitriles by a process involving the steps of halogenating isobutyronitrile (or a beta-substituted isobutyryl nitrile) to alphahalogenated isobutyronitrile, and

subsequently converting the alphahalogenated isobutyronitrile to alkyl acrylic acid derivatives. A further object of the invention is to provide a process for the conversion of the alphachlorisobutyronitrile by dehydrohalogenation to the unsaturated nitrile. Further more specific ob jects are the conversion of the alphachlorisobutyronitrile and the unsaturated nitrile to derivatives of the alkacrylic acids. Other objects and advantages of the invention will hereinafter appear.

According to the present invention the unsaturated compounds above designated may be prepared in the following manner. Isobutyronitrile or a substitution product thereof is halogenated in accord with any suitable halogenating process to obtain the alphahalogenated isobutyronitrile, substantially as illustrated by the formula:

The unsaturated nitrile thus obtained may be treated with an alcohol and water, in the presence of hydrochloric acid, or other suitable mineral acid, such as sulfuric acid, to yield an alkacrylate in accord with the equation:

The alkyl alphachlorisobutyrate maybe then dehydrohalogenated in accord with the process designated under reaction (2) or by any other suitable process to give the alkyl methacrylate substantially in accord with the equation:

A still further method of converting the a lphahalogenated isobutyronitrile to the unsaturated ester may be eifected by treating the nitrile with sulfuric acid and an alcohol in accord with the equation:

In the above formulae R1 designates a substituted or unsubstituted alkylene group, while R designates a substituted or unsubstituted alkyl group.

I shall now describe several examples illustrating my process together with various modifications thereof, but it will be understood that I shall not be limited by the details therein given, unless such limitations are present in the appended claims.

Example 1 Step1 .Chlorine gas is passed into liquid isobutyronitrile at its boiling point, with good mechanical agitation, until the theoretical amount according to the equation has been absorbed. The escaping HCl' gas is passed thru a condenser cooled in an ice and salt freezing mixture to prevent loss of nitrile.

Step 2.The alphachlorisobutyronitrile of step 1 is heated with approximately 4% ferric chloride, at the boiling point of the solution and under 8. suitable refluxing column to obtain the 'methacrylonitrile. The crude methacrylonitrile is washed with water to remove ferric chloride and the ferric chloride free solution distilled.

Step 3.-One mole of methacrylonitrile is added to a solution containing slightly more than one mole of water, one mole of ethanol, and one mole of sulfuric acid, and the resulting solution heated under. reflux to complete the reaction. After separating the precipitated ammonium chloride the unreacted alcohol is removed by distillation. may be purified by fractionation.

Example 2 Step 1.The crude chlorinated isobutyronitrile as obtained from Example 1, step 1, is added to an excess (about 0.5 mole excess per mole of nitrile), containing slightly more than one mole of water, one mole of alcohol, and one mole of HCl per mole of chlorinated nitrile. The HCl solution is made by passing the 'dry HCl gas obtained in chlorinating isobutyronitrile into a solution of methanol and water. The mixture is heated under reflux to complete the reaction. After separation of precipitated NHiCl, the excess methanol is removed by distillation. The

yield of methyl alphachlorisobutyrate is practically quantitative. It may be further purified by distillation.

Stcp 2.Methyl alphachloroisobutyrate obtained in step 1 containing 4% of anhydrous ferric chloride is heated at its boiling point under 9. fractionating column and the distillation regulated so that the temperature at the head is 100-105 C. The crude methyl methaerylate obtained is washed with water to remove HCl, and then distilled.

It will* be appreciated that, generally speaking, when converting the methacrylonitrile or the alphahalogenated isobutyronitrile to the ester of methacrylic acid a number of alcohols may be substituted in lieu of the methyl alcohol designated in the examples and as a result the corresponding ester will be obtained. As examples of these alcohols, are included the aliphatic alcohols, such as methyl, ethyl, propyl, butyl up to and including octyl, decyl, nonyl, and the higher aliphatic alcohols, it being understood that both the normal and branched chain alcohols, whether The ethyl methacrylate obtained primary, secondary, or tertiary, and whether substituted or not, are likewise suitable. Aromatic alcohols may likewise be employed, such, for example, as benzyl alcohol, tolyl alcohol or the aralkyl alcohols, such as the ethyl benzyl, propyl tolyl, etc. It should likewise be real zed that the specific conditions of conducting the halogenation or dehydrohalogenation, as illustrated in the examples, have been found suitable,-higher temperatures, however, may be employed, providing the temperatures be not increased to the point of decomposition of the product. Lower temperatures may be likewise utilized, it being understood that the velocity of the reaction will increase in proportion to the increase or decrease in the temperature.

From a consideration of the above specification it will be realized that many modifications may be made in the details therein given without departing from the invention or sacrificing any of the advantages that maybe derived therefrom. 4

I claim:

1. In a process for the preparation of unsaturated derivatives of isobutyronitrile the step which comprises dehydrohalogenating an alpha halogenated isobutyronitrile to the unsaturated nitrile, utilizing ferric chloride as the dehydrohalogenating catalyst.

'2. In a process for the preparation of methacrylonitrile the steps which comprise dehydrochlorinating alphachlorisobutyronitrile to methacrylonitrile with ferric chloride as the dehydrochlorinating catalyst.

3. In a process for the preparation of a methyl alkyl substituted ketonitrile the step which comprises dehydrohalogenating an alphahalogenated methyl alkyl substituted ketonitrile to the un saturated nitrile with ferric chloride as the dehydrohalogenating catalyst, the reaction being I conducted substantially in accord with the equain which R designates an alkyl group containing not more than two carbon atoms.

DONALD J. LODER. 

